The present invention relates to a hard layer-coated tool used for cutting metal materials, etc., particularly to a hard layer-coated tool having excellent crater wear resistance for use in high-speed cutting and dry cutting.
Cutting tools coated with TiN, Ti (CN), (TiAl)N, etc. are conventionally used widely. However, layers of TiN or Ti (CN) fail to exhibit sufficient oxidation resistance and wear resistance during high-speed cutting. Because a (TiAl)N layer has superior oxidation resistance to that of TiN and Ti (CN), it is used under cutting conditions that a tool edge tip is subjected to high temperatures. However, seizure occurs at a tool edge tip during cutting at high temperatures, failing to achieve sufficient tool life.
JP 2001-293601 A discloses a wear-resistant TiN layer containing fine compound particles of BN, TiB2, TiB, etc. It is described in this reference that these fine compound particles are amorphous and have function to improve the hardness of the layer. Though these fine compound particles contribute to improvement in wear resistance, slidability, seizure resistance, and working precision, this reference fails to teach in detail the properties and form of the fine compound particles.
An object of the present invention is to provide a hard layer-coated tool suitable for a dry cutting operation at a high speed and a high feed, which is provided with improved seizure resistance at high temperatures and suppressed diffusion of elements in a work to a hard coating layer, without sacrificing the wear resistance and adhesion of a hard (TiAl)N coating layer, etc. having excellent oxidation resistance.
As a result of intensive research in view of the above object, the inventors have found that in a tool having a hard coating layer formed on a substrate surface, the layer being made of any of a nitride, a carbonitride, an oxynitride and an oxycarbonitride each containing Ti and B as metal elements, when the hard coating layer is formed such that (a) a boron nitride phase is dispersed, (b) the bonding energy of B and N is observed by ESCA, and (c) the existence of c-BN and/or h-BN is observed by Raman spectroscopy, the lubricating properties of the hard Ti coating layer are improved by the lubricating properties of the BN phase, whereby its crater wear resistance is remarkably improved. The inventors have also found that in a cutting operation in a dry state at a high speed and a high feed, by suppressing a phenomenon of diffusion of elements contained in a work to a hard coating layer, no seizure of a work to a tool occurs and the crater wear resistance of a tool is remarkably improved, resulting in an extremely long tool life. The inventors have further found that necessary to improve the hardness and lubricating properties of the hard coating layer remarkably is not only the addition of B but also the optimization of the coating conditions. The present invention has been completed based on these findings.
Thus, the hard layer-coated tool of the present invention is coated with a hard layer made of any of a nitride, a carbonitride, an oxynitride and an oxycarbonitride each containing Ti and B as metal elements; wherein the hard coating layer contains a boron nitride phase; wherein the bonding energy of B and N is observed in an ESCA analysis of the hard coating layer; and wherein the existence of c-BN and/or h-BN is observed in a Raman spectroscopy of the hard coating layer.
In a preferred embodiment of the present invention, a half-value width Z of a (200) face in an X-ray diffraction of the hard coating layer is in a range of 0.3xc2x0 to 0.6xc2x0; peaks of c-BN and h-BN are detected in an Raman spectroscopy of the hard coating layer; a ratio Q1/Q2 of a peak intensity Q1 of c-BN to a peak intensity Q2 of h-BN is 1.0 or more; and a ratio K/L of a face thickness K to a flank thickness L in the tool is 1.0 or more.
It is preferable that the hard coating layer is formed by using a target of a Tixe2x80x94B alloy; and that the content of B in the hard coating layer is 0.1 to 50 atomic %, based on the total amount (100 atomic %) of metal elements. The hard coating layer may further comprises, as a layer other than the hard coating layer, a hard coating layer comprising at least one metal element selected from the group consisting of Ti, Al and Cr, and at least one non-metal element selected from the group consisting of C, O and N. Part of Al in the hard coating layer containing Ti and Al may be substituted by at least one selected from the group consisting of metals in the Groups 4a, 5a and 6a and Si.
It is preferable that a tool substrate is preferably made of cemented carbide or cermet, and that the total thickness of the hard coating layer is 3 to 15 xcexcm on a tool face. A tool on which the hard coating layer of the present invention can be formed is preferably an insert.